This idea is taken from a 1991 story, which seems very early for this idea. I couldn't find anything like it until at least 1998.

We used to get megabytes of automated invective via email, but that, at least, turned out to be easily fixed; we installed the latest screening software, and fed it a few samples of the kind of transmission we preferred not to receive.

The first recorded instance of a mass-mailing (which was done by mistake) occurred in 1978 when a DEC marketer wanted to trumpet a new feature.

I used company email systems as early as 1986; I don't remember anything like this, because there was no problem. As far as I know, the first use of "spam" to describe repetitive, unwanted email occurred in 1993.

However, Egan is proposing an automated way to remove unwanted email by simply pointing out emails that you don't like. This sounds like "statistical filtering," a technique that was proposed in 1998 and, judging by how well PCs do it, still needs work.